長鏈正高級醇、酸及酯類混合物之非理想表面溶液單分子膜阻止水分蒸發之研究

The Evaporation Resistances of Mixed Monolayers of Non-Ideal Surface Solution of Long-Chain Normal Alcohols, Acids and Esters

10.6623/chem.1969002

呂銘坤(Mong-Kun Lu)；郭人鳳(Jen-Feng Kuo)；顏清脇(Ching-Se Yen)

化學

58年1&2期（1969 / 06 / 01）

7 - 17

繁體中文

以正高級脂肪酸、醇、酯及其各種比率的混合物，溶解於正己烷配製0.0035M溶液，展佈單分子膜於純水面上，保持水溫爲30°C，使用襯鐵弗龍布的水槽、鐵弗龍隔板、Wilhelmy浸板型膜壓計及氯化鋰爲測定水分蒸發速率的吸濕劑，研討水分子在單成分及混合單分子膜中之擴散現象。測定單分子膜抑阻水分蒸發效果，並計算膜壓與蒸發比阻的關係。由實驗結果得知，酸及醇分子的碳鏈愈長，其蒸發比阻愈高。酸與醇、酸與酯或醇與酯的双成分單分子膜呈非理想表面混合物。其蒸發比阻與理想表面混合物偏差之大小及正負依單分子膜的種類，成分之克分子比及膜壓而定。當純醇單分子膜的蒸發比阻大於純酸單分子膜的蒸發比阻時，由此二者所組成之混合物呈正偏差，相反時，呈負偏差。呈正偏差之醇與酸混合物，在膜壓爲10 dyne/cm時其偏差恰爲零。由酸與酯或醇與酸所組成之混合物，皆産生大的偏差。偏差之大小可用超越活化能表示之。

The rate of evaporation of water was studied by spreading monolayers of n-hexadecanol, n-octadecanol, n-eicosanol, stearic acid, palmitic acid, ethyl stearate, and their mixture on pure water surface. The work was conducted by using a precisely developed Wilhelmy dipping plate type film balance. The film balance consisted of movable Teflon barriers and a Teflon lined trough instead of conventional Langmuir trough. The rate of evaporation of water was measured by the rate of absorption of water vaper by solid lithium chloride desiccant supported above the water surface The water in the trough was kept at 30℃. The specific resistance of mixed monolayers of n-long-chain alcohols and acids deviated from the ideal mixture law which is the linear relation between logarithm of specific resistance and the molar composition. When the specific resistance of pure alcohol monolayer was greater than that of pure acid monolayer, the mixed monolayer behaved postive deviation. As the nonideal surface solution was positive deviation, it behaved ideally at film pressure of 10 dyne/cm. On the other hand, the specific resistance of pure alcohol monolayers was smaller than that of pure acid mono layers the mixed monolayers appeared negative deviation. The specific resistances of mixed monolayers of ethyl-stearate and n-octadecanol or ethyl-stearate and stearic acid deviated far from ideal case. Nonideal behavior of these mixed monolayers also can be expressed in term of excess surface activation energy.